1. Field of the Invention
This invention relates generally to a novel method for improving yields in hydrosilation reactions. More particularly, this invention relates to an improved method for preparing methacryloxy and acryloxy containing organosilanes and organosilicones under certain conditions without the unwanted polymerization, i.e., gellation, generally associated with the reactions involving these compounds. The process is further improved when a stabilizer is used to obviate some of the specific conditions required to avoid gellation.
2. Prior Art
The hydrosilation reaction, the addition of silicon hydrides to unsaturated compounds, is the most common method for the preparation of organosilicon compounds with functional groups in the organic position of the molecules. There are numerous literatures which teach how to carry out hydrosilation reactions with various unsaturated compounds such as alkenes, unsaturated ethers, amines, etc. 1 C. Earborn and R. W. Bott, Organometallic compounds of the Group IV Elements (1968).
These methods, however, are not suitable for the preparation of compounds containing methacryloxy, CH.sub.2 .dbd.C(CH.sub.3)COO--, and/or acryloxy, CH.sub.2 .dbd.CHCOO--, functional groups. This is because, unlike the other organosilicon compounds, methacryloxy and acryloxy containing organosilicon compounds can polymerize easily during preparation and/or purification through reaction of the methacrylate double bonds. Such polymerization not only results in wasted products, but also renders clean up very difficult, if not impossible, because of the gelled product inside.
U.S. Pat. No. 3,258,477 to Plueddemann et al. teaches the preparation of a stable .gamma.-methacryloxypropyltrimethoxysilane by simultaneously charging both trimethoxysilane and allyl methacrylate into a toluene solution containing 2,5 ditertiarylbutylhydroquinone, additional trimsthoxysilane and a solution of chloroplatinic acid all at 105.degree. C. The use of large amounts of toluene as a solvent, however, makes this process rather expensive and economically unattractive.
In U.S. Pat. No. 4,276,426 to Lindner et al., .gamma.-methacryloxypropyltrichlorosilane was again prepared without gellation when trichlorosilane, allyl methacrylate and platinum catalyst were continuously introduced into a pipe-shaped reactor and circulated in the reactor while the reaction mixture was continuously being removed from the reactor. In this reference, the improvement of the process comprised continuously circulating the reaction mixture in the reactor at at least 1000 centimeters per minute. The contents of the reactor will gel when the contents are not continually circulated, i.e., this process cannot be carried out as a batch process.
Thus, there is no teaching in the prior art of a process to halt the undesirable polymerization caused by methacryloxy and acryloxy containing organosilicon compounds which process does not require either the use of large amounts of solvents or the continuous circulation of the reaction product mixture. There is a need in the art for a more economic and more expedient process for preparing these compounds. Further, there is a need to insure undesirable polymerization does not occur during preparation, purification or storage of the compounds.